The present invention relates to an electric governor for a fuel injection pump of an internal combustion engine or a diesel engine in particular.
In a conventional electric governor, a sensor of an electromagnetic pickup including a permanent magnet wound with a coil for detecting the engine speed is generally provided in opposition to a ring gear of the engine or a gear made of a magnetic member rotating at a speed proportional to the engine speed on the governor. Each time the tip of the gear of the magnetic material passes the sensor of the electromagnetic pickup, the magnetic fluxes change and an AC voltage of a frequency proportional to the engine speed is induced in the coil of the electromagnetic pickup, thus making it possible to produce a signal changing in accordance with the engine speed from the electromagnetic pickup.
The conventional electric governors have only one electromagnetic pickup for reasons of cost and mountability, and in the case where normal detection of the engine speed becomes impossible due to such troubles as the breakage of the coil of the electromagnetic pickup, the breakage of the wire harness connecting the electromagnetic pickup and an electric control circuit for determining the injection amount or ill contact of the connector, the engine is stopped by a safety mechanism including the electric control circuit.
In the event that the electromagnetic pickup fails to produce a signal changing with the engine speed for some faults, therefore, the conventional electric governor is such that the engine is stopped by the electric control circuit, thus making impossible the powered running of the automobile to a passing place on a freeway or in a wide open area.